The invention relates to a piston ring for the piston of an internal combustion engine, having a circumferential chamfer lying on the inside, the size of which decreases symmetrically to an axis that lies radially and runs through the ring joint, on both sides of the ring joint, all the way to the side of the piston ring that lies opposite to the ring joint.
A piston ring for the piston of an internal combustion engine, having a circumferential chamfer lying on the inside, the size of which decreases constantly, proceeding from the ring joint to the side of the piston ring that lies opposite to the ring joint, and which chamfer is disposed on the upper side of the piston ring, is known from the U.S. Pat. No. 2,591,920. A chamfer that lies on top and on the inside has the effect that the piston ring experiences a positive twist under mechanical stress, i.e. that when this happens, the upper side of the piston ring is given a conical shape that opens toward the top. In this way, the outer edge of the upper ring groove wall makes contact with the upper side of the piston ring, so that an improved seal of the piston ring relative to the combustion gases of the combustion chamber, which are under pressure, is achieved in this region.
In the event of positive twisting of the piston ring, the lower, inner edge of the piston ring makes contact with the lower ring groove wall, thereby causing a circumferential gap to form, which becomes ever narrower radially on the inside, and leads to a poor sealing effect of the piston ring relative to the oil stripped off from the inner cylinder wall by its outer, lower edge.